Rotary compressor for refrigerating apparatus



March 12, 1940. HULL AL 2,193,250

ROTARY COMPRESSOR FOR REFRIGERATING APPARATUS Filed Nov. 6, 1937 2 Sheets-Sheet l Patented Mar. 12, 1940 UNITED STATES PATENT OFFICE ROTARY COMPRESSOR- FOR- REFRIGERAT- ING APPARATUS Harry B. Hull and Alex A. McCormack, Dayton,

Ohio, assignors to General Motors Corporation, Dayton, Ohio, a corporation of Dela- Application November 6, 1937, Serial No. 173,222 2 Claims. (01. 230-147) This invention relates to refrigerating apparatus and more particularly to rotary compressors for refrigerating systems and motor-compressing purposes.

and a means for employing the spaces between the impeller and the two sides of the groove as the first and second stages of multi-stage compression. This is done by causing the gas to be 5 While the advantages of rotary compressors drawn into the chamber surrounding the impel- 5 have long been recognized, there has always been ler and pumped into a chamber within the imconsiderable difliculty in preventing leakage in peller from which the gas is pumped into a chamrotary compressors where relatively high pres ber between the impeller and the inner edge of sure differences are encountered. This is bethe groove and thence into the casing enclosing cause of the fact that it is difllcult to maintain the motor and compressor. 10 a tight seal in a rotary compressor, since lubri- Referringnow to the drawings and particularly cant must be used as a seal and there is a com- Fig. 1, there is shown a refrigerating system inparatively small area of contact for preventing eluding a sealed motor-compressor unit generalleakage. When there is an excess pressure dif- 1y designated by the reference character 20 for ferential upon the rotary compressor, the gas compressing the refrigerant and for forwarding l5 willbreak through the film of lubricant and leak the compressed refrigerant through conduit 22 back from the high side to the low side, thereby to a condenser 24 where the condensed refrigerreducing the efiiciency of the compressor and ant is liquefied and collected in a receiver 26. making it impossible to maintain high pressure From the receiver 26, the liquid refrigerant is differentials. forwarded through a supply conduit 28 to an It is an object of our invention to provide 8. expansion valve 30 which controls the flow of rotary compressor which can operate at relativeliquid refrigerant into an evaporating coil 32 ly high pressure differentials. located within an insulated ice cream cabinet 34 It is another object of our invention to provide surrounding the ice cream cans 36. The refrigi an extremely simple rotary compressor, having erant evaporates within the evaporator coil 32 a high efficiency, which will compress gas under under reduced pressure and is returned to the relatively high pressure differentials. compressor through the return conduit 38. The

It is another object of our invention to provide operation of the motor-compressor unit is cona rotary compressor of the oscillating eccentric trolled by a snap-acting switch means 40 operat- 80 type which is capable of operating under a high ed by the thermostat bulb 42 located upon the pressure difl'erential. evaporating coil 32 within the ice cream cabi- It is a further object of our invention to pronet. vide an extremely simple two-stage rotary com- In order to simplify the p essor pressor employing but a single impeller. unit, we employ a sealed rotary motor-compres- It is another object oLour invention to provide sor unit. This motor-compressor unit includes a well-balanced two-stage rotary compressor. an inverted cyl nd a Casting P o ded w t Further objects and advantages of the present integral cooling fins On s Outer a d having invention will be apparent from the following dean inner cylindrical chamber 46 provided with scrlption, reference being had to the accompanyan open bottom and a small side inlet chamber ing drawings, wherein a preferred form of the 48. The chamber .46 is closed by the bottom 40 present invention is clearly shown. a casting 50 held in place by a. ring 52 which is In the drawings: fastened by screws 54 extending through the ad- Fig. 1 is asectional view of amotor-compressor Jacent flange portion of the casting 44.

, unit taken along the line l-I of Fig.2 embody- Within the casting 44 is placed a stator 56 5 ing our invention and a partly sectional and of an electric conduction motor which is held partly elevationalview of the remaining parts of in place by a press fit in the casting and by long a refrigerating system for an ice cream cabinet; screws 58 which pass through the laminations Fig. 2 is a sectional view taken along the line of the stator. The rotor 60 is of the usual in- 2-2 of Fig. 1; and duction motor type and is fitted onto a drive 60 Fig. 3 is a sectional view taken along the line shaft 62 having its lower end mounted in a bear- 3-3 of Fig. 2.

Briefly, we have shown a refrigerating system for an ice cream cabinet including a motor-compressor unit of the rotary type having a groove; an impeller, a divider block for sealing the groove,

ing 4 which fits into a boss 66 extending upwardly from the bottom casting 50. The upper end 'of the drive shaft 62 is supported bya bearing 8 fitted into the horizontal wall 10 of the casting 44. This horizontal wall I0 is provided with an annular groove I2 surrounding the bearing 68.

An'oscillatable member I4, commonly called a divider block; fits into arc-shaped notches in the opposite walls of the groove 12 in order to provide a seal extending across the groove. An impeller I6 is provided with a rather large arcshaped projection I8 extending nearly 360 which fits into the groove 12 and is adapted to make sealing contact with the bottom of the groove. This projection is notched so as to receive the divider block I4 upon its opposite plane faces. This projection I8 has an outer diameter slightly less than the outer diameter of the groove 12, while its inner diameter is slightly greater than the inner diameter of the groove 12.

The impeller I6 is provided with an outer flange 80 which makes sealing contact with a machined face 82 upon the upper face of the casting 44. The impeller I6 also has an inner flange 84 adapted to make sealing contact with the machined top surface of the casting 44 upon the inside of the groove 12. The flange 84 also receives the outer race of a ball bearing 88 having its inner race fitted onto an eccentric projection 90 of the drive shaft 62. This eccentric projection 90 is provided with a threaded extension 92 which is concentric with the drive shaft 62. A balance weight 94 is fastened onto the end of the eccentric projection 90 by a nut 96 which is threaded onto the threaded extension 92 in order to hold the balance weight 04 in place. The center of mass of the balance weight 94 is diametrically opposite the center of mass of the eccentric projection 90 and the impeller I6. In this way, the eccentric mass of the balance weight will balancethe eccentric mass of the impeller and the eccentric. This portion of the compressor'is enclosed by a top casting I02 which is fastened onto the top of the casting 44 by screws I04.

The refrigerant enters the motor-compressor unit through a plug I06 which closes the bottom of the chamber 48. This plug is provided with a check valve I08 held in place by a cage H0. The gas flows through chamber 48 to a horizontal passage I I? which extends to the inside of the groove I2 directly adjacent the divider block I4. Upon the opposite side of the divider block, the impeller is provided with a horizontal passage H4 which extends into a groove II8 provided in the bottom of the projection I8 of the impeller. A check valve I is provided at he outlet of the passage II4 to prevent gas from flowing from the groove II8 back into passage H4. The passage I22 extends from the groove II8 to the inner face of the projection I8 of the impeller I6. The impeller 16 is also provided with an outlet passage I24 provided with a check valve I26 which permits the flow of gas out of the inner chamber into the chamber formed beneath the top casting I02 from which the gas Passes through the tube I26 into the motorgenerator. Atapped hole I28 in the side of the casting 44 connects the motor chamber with the supply conduit 22.

When the motor operates, the impeller is oscillated by its eccentric so that it begins its movement in contact with the outer wall of the groove adjacent the outlet of the passage H2, and this point of contact gradually moves around the outer wall of the groove pushing gas ahead of this point of contact until the point of contact reaches the other side of the divider block where the passage II 4 is located. As this point of contact moves around the outer wall of the groove 12, the gas is pushed ahead of it between the outer wall of the groove and the outer wall of the impeller through the passage II4 past the check valve I 20 into the groove I I8. The groove II8 serves as the intermediate pressure chamber and contains the gas which has been compressed in its first stage between the outer wall of the impeller and the outer wall of the groove. The gas then passes through the passage I22 into the space between the inner wall of the groove and the inner wall of the impeller.

The gas is first admitted into this inner chamber; and, after the point of contact between the Outer walls of the impeller and the groove has moved to a point opposite the divider block, the passage I22 is closed and the second stage compression is begun in the inner chamber between the inner walls of the groove and the impeller. This second stage compression is completed in slightly less than 360 degrees of rotation, and

throughout the latter portion of this rotation the gas is forced out through the passage I24 past the check valve I26. It should be noted that the second stage compression is completed when the first stage compression is near the middle of its stroke and the higher fluid pressure upon the smaller inner wall of the impeller is approximately balanced by the lower fluid pressure upon the larger outer wall.

The capacity of the two chambers may be proportioned by the relative diameter of the two chambers, which is governed by the thickness of the projection I8 of the impeller 16. Preferably, the capacities are so adjusted that the pressure within the intermediate chamber, that is in the groove H8, is substantially a mid point be tween the suction and discharge pressures.

While the form of embodiment of the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A rotary compressor comprising a stationary member and an impeller member, said stationary member being provided with an annular recess, said impeller member being located within said recess dividing said recess into inner and outer pumping chambers, means for oscillating said impeller member to move gas around the recess upon the inside and the outside of the impeller member, means for providing a seal extending across said recess in sealing engagement with said impeller member, the portion of said impeller member within said recess bein provided with a cavity of large volume, said impeller being provided with a passage forming the outlet of one of said pumping chambers and leading directly into said cavity, said impeller being provided with another passage forming the outlet of said cavity and leading directly into the inlet portion of the other pumping chamber.

2. A rotary compressor comprising a stationary member and an impeller member, said stationary member being provided with an annular groove and flat surfaces extending along the edges of the groove, said impeller member being provided with a portion extending to and making sealing engagement with the bottom of the groove divide ing said groove into inner and outer pumping chambers, said extending portion having a thickness less than the width of the groove, said impellerhaving another portion making sealing engagement with said flat surfaces, means for aieaaso 3 tion of one of said pumping chambers and said cavity, said impeller member being also provided with a passage connecting said cavity and the inlet of the other pumping chamber, and means for oscillating the impeller to pumpfluid from one chamber into the cavity and thence into the other chamber.

HARRY B. HULL.

ALEX A. MCCORMACK. 

